Spring of coiled flat



y 1962 J. A. FREY ETAL 35,

SPRING OF COILED FLAT Filed Nov. 24. 1959 INVENTORS JOHN A. FRE'Y and JOHN A. HE/VR/C/(SON A llarney United States Patent Ofrfice 3,035,826 Patented May 22, 1962 This invention relates to improvements in springs of coiled flats and the method of making the flats therefor.

In springs formed of coiled flats such as are used in door checks and the like, the efliciency of the spring action is limited by friction between the coils thereof. Such springs have heretofore been formed with a crown to minimize friction but this necessitated forming the strip in a single strand in order to roll a crown into the strip which adds considerably to the cost thereof.

'It is accordingly an object of this invention to provide a method of making flats for coiled springs at a lower cost than was heretofore possible.

It is another object of this invention to provide a spring of coiled flat having a reduced frictional component.

The foregoing and further objects will be apparent from the following specification when read in conjunction with the attached drawing, wherein:

FIGURE 1 shows a length of spring flat material of our invention;

FIGURE 2 is a side view of a coiled spring formed from the material of FIGURE 1; and

FIGURE 3 is a section on line Ill-III of FIGURE 2.

Referring more particularly to the drawing, the numera1 2 designates a length of strip suitable for forming into flats for coiled springs. Pursuant to the teachings of our invention, the strip is sufliciently wide to form a plurality of flats F for coiling. Accordingly the strip can be efii- -ciently rolled in any desired Width. After rolling the strip can be conveniently slit into suitable widths for spring flats. In accordance with the teachings of our invention, the flat is provided with a purality of ribs or ridges 4 on one side extending along the length thereof.

For most applications a minimum of 3 ridges should be provided on each spring flat. The maximum number is not critical but should in general be equal to the width of the flat in inches divided by 2 times the ridge width in inches. Height of the ridges may vary from about .0015 as a minimum to approximately 10% of the strip thickness. For example on .060" thick material, the height may vary from .0015" to .006. The width of the ridge may vary from a minimum .006" to a maximum of approximately 10 times the ridge height.

Not only does the use of ribs or ridges on the flats provided by our invention increase the efliciency of coiled springs formed therefrom but the marked decrease in efiiciency after cycling requiring resetting of conventional springs is almost completely eliminated. This unexpected result is clearly shown by the following energy loss tests.

In these tests on conventional doorcheck springs and ribbed springs of this invention, torque-twist curves were autographically plotted in the windup and unwind direction and the area of the hysteresis loop formed was meas- Rlbb Rib ured with a planimeter. The area under the hysteresis loop was measured (1) when a torque of 117 inch-pounds was obtained on the curve, (2) when a twist of 300" was reached on the curve, and (3) when an initial energy of 328 inch-pounds was stored under the curve. These three methods of comparison were used because the conventional crowned spring did not develop the same torque for the same twist as the ribbed spring.

The springs were then cycled 48 times and the same energy loss per cycle was measured.

TABLE I Before Cycling, inch-lbs.

Aiter Cycling, inch-lbs.

Conventional MEASURED TO A TWIST OF 300 Conventional Ribbed 28. 8

Conventional 48 5 31. 8 bed 34. 0 29. 5

The loss in energy per cycle for a standard crowned spring was 14.8% and after cycling 9.9%, whereas the ribbed spring of our invention lost 10.4% before cycling and only slightly less, i.e., 9.0% after cycling.

While we have shown and described several specific embodiments of our invention, it will be understood that these embodiments are merely for the purpose of illustraition and description and that various other forms may be devised within the scope of our invention, as defined in the appended claim.

We claim:

A coiled spring composed of a spring flat having at least three continuous longitudinally extending ribs on one side thereof, the outermost of said ridges being spaced inwardly from the edges of the flat, the other side of said flat being substantially flat, the height of said ribs being between .0015 and about 10% of the thickness of said spring flat, said ribs providing substantially line contact with the flat side of said spring flat.

France May 13, 1940 Germany Feb. 11, 1952 Germany Jan. 22, 1953 Great Britain June 4, 1924 

